docstr: Add an edge between two layers.
  
  Parameters
  ----------
  from_layer : Layer
      the layer with the outbound connection
  to_layer : Layer
      the layer with the inbound connection
docstr_tok: ["Add","an","edge","between","two","layers",".","Parameters","--","--","--","--","--","from_layer",":","Layer","the","layer","with","the","outbound","connection","to_layer",":","Layer","the","layer","with","the","inbound","connection"]
code: def add_edge(self, from_layer, to_layer):
      """
      Add an edge between two layers.
  
      Parameters
      ----------
      from_layer : Layer
          the layer with the outbound connection
      to_layer : Layer
          the layer with the inbound connection
      """
      id_to = id(to_layer)
      id_from = id(from_layer)
      if id_to not in self.__layers_by_id:
          raise ValueError(
              f"Inbound layer {to_layer} not found in network."
          )
      if id_from not in self.__layers_by_id:
          raise ValueError(
              f"Outbound layer {from_layer} not found in network."
          )
      self.__graph.add_edge(id_from, id_to)
  
file_path: OMLT/src/omlt/neuralnet/network_definition.py
imports: import networkx
  from omlt.neuralnet.layer import Layer
label_desc: Use image node_id 3 for calling the NetworkDefinition obj's underlying member method code with example usage: obj.add_edge(from_layer, to_layer) without return types